This invention concerns diesel engines, and more particularly secondary fuel injection systems for turbocharged diesel engines.
Such secondary fuel injection systems have heretofore been devised to increase the power and torque output of an engine. Secondary fuels, in particular propane, act as a catalyst to enhance the combustion of diesel fuel to increase power and reduce emissions, as well as to improve engine fuel economy. Diesel engines are commonly turbocharged to increase the power output of the engine by delivering compressed air into the engine cylinders. The degree of turbocharger compression of the air would change the rate of secondary fuel injection required for a desired degree of power enhancement.
U.S. Pat. No. 4,953,515 describes a secondary fuel injection system in which an arrangement of switches and valves varies the rate of secondary fuel injection in stepwise fashion as the boost pressure reaches predetermined increased levels in order to approximate the proper rate of secondary fuel injection at each level.
This arrangement is complex as it requires a number of switches and valves, and is thus vulnerable to malfunction. In addition, the stepwise operation precludes smooth operation and only approximates the proper rate of propane fuel injection.
Another problem with such secondary fuel injection systems involves positive control over the system. If the system is activated by turning on the ignition switch, any leakage in the valves and lines could occur caused by static pressurization thereof without the engine being operated. The leakage could accumulate dangerously during servicing of the engine with the ignition switch on.
Furthermore, if the vehicle is operated by someone unaware of the pronounced power enhancing effect of the system, the unexpected power boost could create the possibility that loss of control of the vehicle powered by the engine equipped with the secondary fuel injection system could result.
Accordingly, it is an object of the present invention to provide a secondary fuel injection system for turbocharged diesel engines which automatically controls the rate of secondary fuel injection to be closely matched to the boost air pressure, using a relatively simple and reliable set up.
It is another object of the present invention to provide an arrangement for manually controlling initiation of the operation of such a secondary fuel injection system which insures against inadvertent activation of the system when the engine is started, or unwanted activation when the ignition switch is turned on without starting the engine.
These and other objects of the present invention which will be understood upon a reading of the following specification and claims are achieved by utilizing a diaphragm regulator valve to control the pressure of gaseous propane from a pressurized tank of the gaseous secondary fuel introduced into the air inlet line to the turbocharger. The boost air pressure is applied to one side of the diaphragm so that the flow rate is varied continuously in proportion to changes in the boost air pressure, thereby maintaining a proper rate of propane injection depending on the power output of the engine.
A failsafe switching arrangement insures safe operation of the secondary fuel injection system, which includes wiring the arrangement into the vehicle ignition so as to be turned off whenever the ignition switch is turned off.
In addition, a manually positioned on/off switch is combined with a xe2x80x9cmomentary onxe2x80x9d switch booth required to be set to an on condition for the secondary fuel injection system to be activated. The xe2x80x9cmomentary onxe2x80x9d switch is reset to an off condition whenever the vehicle ignition or the manual switch is turned off, requiring a manual push reset to the on condition after the other switches are turned back on.
This arrangement insures that an additional positive action by the vehicle operator is required to activate the system after the ignition switch and manual switch are turned on.